SQL Remote only currently uses three characters in the extension for messages files for the FILE, FTP and HTTP message system, and we limit the characters to alpha-numeric character. Because of that, the maximum number of messages that one database can send to another database in the system is 36 + 36*36 + 36*36*36 = 47988. At the default message size of 50K, that allows for approximately 2GB of SQL statements to be pending in the message system.

If you reach the maximum number of messages, you will need to either increase the message size, or convince your remote databases to pick up messages more often.

36*36*36 is correct if SQL Remote only used three digit extensions, but SQL Remote will first use files with a single character extension (.0 -> .z), and then two character extensions as well (.00 -> .zz), so that's why we need to add another 36 + 36*36.